SEARCH · Engineering Papers

Results for “Guidelines”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41

All sources NASA NTRS DOE OSTI

DOE OSTI2024

DaYu: Optimizing Distributed Scientific Workflows by Decoding Dataflow Semantics and Dynamics

The combination of ever-growing scientific datasets and distributed workflow complexity creates I/O performance bottlenecks due to data volume, velocity, and variety. Although the increasing use of descriptive data formats (e.g., HDF5, netCDF) helps organize these datasets, it also creates obscure bottlenecks due to the need to translate high level operations into file addresses and then into low-level I/O operations. To address this challenge, we introduce DaYu, a method and toolset for analyzing (a) semantic relationships between logical datasets and file addresses, (b) how dataset operations translate into I/O, and (c) the combination across entire workflows. DaYu's analysis and visualization enables identification of critical bottlenecks and reasoning about remediation. We describe our methodology and propose optimization guidelines. Evaluation on scientific workflows demonstrates up to 3.7x performance improvements in I/O time for obscure bottlenecks. The time and storage overhead for DaYu's time-ordered data is typically under 0.2% of runtime and 0.25% of data volume, respectively.

Tang, Meng↗

DOE OSTI2021

Comparison of Simulation of Dual-Active Bridge in Different Simulators and Using Different Simulation Methods

The accuracy of states measured from simulation of a dual-active bridge (DAB) converter with an open-loop controller has been used for comparing simulation software and algorithms. The accuracy of the measured states is sensitive to simulation settings and parameters chosen. In this paper, the simulation of the DAB converter with open-loop control is run in the MATLAB/Simscape Electrical, PLECS, and PSCAD software environments, with various simulation settings. The simulation results are also compared with a new simulation algorithm proposed for DAB simulations. Different simulation settings are evaluated, including different solver types, operating conditions, and the on-state resistance values of the MOSFET switches. The simulation results are compared with the theoretical calculations. It is shown that unexpected divergence and DC offset may occur in some cases. This paper provides guidelines to simulate the DAB converter with open-loop control.

Yin, Shiyuan↗

DOE OSTI2020

A Sensorless Coil Detection Scheme based on Dead-Time Effect in Dynamic Wireless Power Transfer Systems

The detection of electric vehicles in dynamic wireless power transfer (DWPT) systems is important to reduce the standby losses and comply with the electromagnetic-field emission guidelines recommended by the International Commission for Non-Ionizing Radiation Protection. This paper discusses a novel sensorless coil detection scheme, which exploits the phenomenon of voltage-polarity reversal/notches caused by the dead-time effect in the full-bridge inverter. The variations in the system impedance and dead-time effects are collectively exploited to detect the receiver coil in the DWPT system. The proposed coil detection scheme is accomplished at low excitation voltage, which reduces the inverter standby losses. The theoretical analysis of the notch occurrence and open-loop simulation results are presented using a DWPT model developed in the piecewise linear electrical circuit simulation software.

Kavimandan, Utkarsh↗

DOE OSTI2020

Shield Design for 50 kW Three-Phase Wireless Charging System

In this paper, magnetic field emissions (MFE) from a 50 kW bipolar coil-based three-phase wireless charging system (WCS) is investigated. Then, a shield design is proposed to suppress the MFE below the safety limit identified by the International Commission of Non-Ionized Radiation Protection (ICNIRP) guidelines. Bipolar coil-based three-phase (3φ) WCSs provide extremely high power-density; therefore, the 3φ WCSs are highly promising for high-power fast-wireless-charging of the electric vehicles. For the high-power EV application, it is a critical challenge to design a shield to suppress the MFE below the safety limit. The traditional aluminum shield is found ineffective for the bipolar 3φ-WCS. The proposed shield is designed with high-permeability magnetic material, i.e. ferrite, nanocrystalline material, etc. The proposed shield is simulated in finite element analysis (FEA) and the FEA results show that the proposed magnetic shield effectively suppresses the magnetic field emission below the ICNIRP limit. The generalized design of the proposed shield can be used for even higher power bipolar coil based WCSs.

Mohammad, Mostak↗

DOE OSTI2021

Angle Droop Design for Grid-Forming Inverters Considering Impacts of Virtual Impedance Control

Grid-forming inverters (GFMs) based on active power-frequency droop control and reactive power-voltage droop control have been developed in recent years, which can generate voltage and frequency references for islanded power systems or microgrids to improve system-wide synchronization and power-sharing capability. It is known that the control delays in GFMs may cause system harmonic instability. To eliminate this issue, virtual impedance techniques are normally adopted. This paper gives a comprehensive examination of the impacts of virtual impedance control block Z v in GFMs on system stability. It is revealed that although Z v is effective in eliminating system harmonic stability, it may ruin system synchronization stability as a side effect. To compensate for the negative impacts caused by Z v , an active power-angle control block is added into the conventional droop control. Design criteria are also proposed accordingly to ensure system stability over the entire frequency range. Simulations and experimental testing are conducted to validate the analysis and the proposed design guidelines. It can be concluded that the Z v control-caused grid-synchronization instability issues can be eliminated with an appropriate active power-angle droop design.

Kong, Le↗

DOE OSTI2022

A Fast-Response High-Accuracy Overvoltage Protection Circuit for Soft-Switching Current-Source Converters

Although voltage-source converters (VSCs) have been a focus of research for decades and are widely applied in numerous applications, they face great challenges in short-circuit failures, high dv/dt and electromagnetic interference (EMI), especially using wide bandgap devices. Instead, current-source converters (CSCs) are attracting increasing attention in recent years owing to their friendliness to short-circuit faults, improved EMI, etc. For CSCs, overvoltage is the most catastrophic failure since the semiconductor devices can hardly withstand an overvoltage for a short pulse. In this paper, a fast-response high-accuracy overvoltage protection (OVP) circuit is proposed to protect CSCs from overvoltage damage. It also features a small form factor, good noise-immunity, friendly retrofit capability, and no need for active switches. In this paper, the operating principle and design guideline of the proposed OVP circuit is introduced. Its effectiveness is validated in soft-switching solid-state transformer (S4T) at 500 V. In experiments, the voltage detection error of less than 5% and a propagation delay of fewer than 400 ns have been achieved.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2024

Deep Learning-enhanced Block-Diagram Modeling of Solar Power Systems

Data-driven models of power system inverter-based resources are desired to run simulations faster than with detailed electromagnetic transient models, to hide proprietary design details, to support control system design applications, and to aggregate the effects of distributed energy resources. This paper applies a customized Hammerstein Wiener framework to train block diagram models from thousands of electromagnetic transient simulations or experimental test records. The block diagram models integrate with larger grid simulations as voltagecontrolled current sources or current-controlled voltage sources for several simulators. Guidelines for block architecture and training are presented. Three-phase balanced, three-phase unbalanced, and single-phase examples all achieve an acceptable root mean square error of no more than 0.05 per-unit.

Mcdermott, Thomas E. [Private consulting company]↗

DOE OSTI2022

F*** workflows: when parts of FAIR are missing

The FAIR principles for scientific data (Findable, Accessible, Interoperable, Reusable) are also relevant to other digital objects such as research software and scientific workflows that operate on scientific data. The FAIR principles can be applied to the data being handled by a scientific workflow as well as the processes, software, and other infrastructure which are necessary to specify and execute a workflow. The FAIR principles were designed as guidelines, rather than rules, that would allow for differences in standards for different communities and for different degrees of compliance. There are many practical considerations which impact the level of FAIR-ness that can actually be achieved, including policies, traditions, and technologies. Because of these considerations, obstacles are often encountered during the workflow lifecycle that trace directly to shortcomings in the implementation of the FAIR principles. Here, we detail some cases, without naming names, in which data and workflows were Findable but otherwise lacking in areas commonly needed and expected by modern FAIR methods, tools, and users. We describe how some of these problems, all of which were overcome successfully, have motivated us to push on systems and approaches for fully FAIR workflows.

Wilkinson, Sean↗

DOE OSTI2022

Instrumentation for Assessing DC Electrical Distribution Systems in Buildings

Direct current (DC) distribution systems is emerging as a favorable option over alternating current in buildings due to its energy and non-energy benefits (e.g., efficiency, resilience, safety). However, limited guidelines exist to evaluate the DC electrical distribution infrastructure. This paper aims to fill that gap by detailing our experience with metering a building-level electrical DC distribution system. Our case study is a DC microgrid at the Direct Energy Partners Research & Development facility located in Charlotte, North Carolina. This paper presents our approach, technical challenges, and lessons learned with DC metering and instrumentation.

buildings↗

DOE OSTI2022

An Experiment-based Distribution Level Performance Comparison among PMUs

This paper presents a experiment-based distribution level performance comparison among three Phasor Measurement Units (PMUs). Several evaluation criteria, including the total vector error, the phase angle error, the frequency error, the rate of change of frequency, the response time, the settling time, the overshoot, and the algorithm window size, are selected to compare the static and dynamic performances of the PMUs under steady state and step response test conditions. In order to have a more realistic test environment, a test is setup in which PMUs under evaluation have exactly the same input signals. The quantitative experiment result analysis gives an end-user guideline to the PMU selection regarding distribution level applications.

Yin, He↗

DOE OSTI2020

A Flexible and Secure Evaluation Platform for Overvoltage Protection in Power Electronics Systems

This paper summarizes the fault mechanisms specifically for the overvoltage protection schemes in power electronic converters and the resulted power electronics enabled systems. A flexible and secure evaluation platform for overvoltage protection, has also been presented based on this conceptual mechanism. The proposed platform aims at testing the protection performance of distinctive overvoltage protection schemes. It would be applied to verify the effectiveness, identify potential strengths and weaknesses, and obtain the most critical protection response time to provide sufficient engineering insights for the designer. The operation principle and detailed design guideline have been presented first. The comprehensive component stress has been analyzed. An intensive set of LTSpice simulations have been conducted to show the validity of the proposed assessment approach.

Zheng, Sheng↗

DOE OSTI2020

Review of Safety and Exposure Limits of Electromagnetic Fields (EMF) in Wireless Electric Vehicle Charging (WEVC) Applications

This study reviews the exposure limits and safety of intermediate frequency (IF) electromagnetic field (EMF) emissions for wireless electric vehicle charging (WEVC) applications. A review of the electromagnetic field exposure limits identified in international guidelines are presented. An overview of the electromagnetic field shielding technologies is provided including recommended geometries, materials, and performances of the methods available in the literature. Available laboratory results of EMF emissions are summarized considering several wireless power transfer studies in different power levels. Possible EMF reduction techniques are discussed with shielding practices and ORNL case studies. Also, living object detection (LOD) and foreign object detection (FOD) methods are reviewed from a safety aspect.

Asa, Erdem↗

DOE OSTI2020

Design of a 100 kW Surface Permanent Magnet Machine with Wide Constant Power Speed Ratio for Traction Applications

Surface permanent magnet (SPM) machines are considered to be strong candidates for traction applications due to their high power density and high efficiency. By adopting fractional-slot concentrated windings, SPM machines can achieve a wide constant power speed range. A carbon fiber sleeve is applied to ensure the retainment of the magnets at high speed operating conditions. The purpose of this paper is to present the design of a high speed SPM machine for traction applications with 25 kW/Liter active power density and a wide constant-power speed range that is consistent with guidelines and targets presented in the Electrical and Electronics Technical Team Roadmap published by the US Department of Energy. The predicted electromagnetic performance and structural characteristics are presented based on both analytical and FEA results.

42 ENGINEERING↗

DOE OSTI2023

Echogenic Segmentation for Ultrasonic Measurements of Spatially Distributed Properties in Solids

An ultrasonic (US) pulse propagating between transducer-receiver responds cumulatively to distributed material properties it encounters, such as temperature distribution. Such convolution makes the unique reconstitution of distributions impossible short of applying tomographic techniques. However, spatial heterogeneity in material properties is readily revealed by segmenting the US propagation path with echogenic features (EF), producing a train of echoes delayed as a function of segmentally localized properties. Unfortunately, in low attenuating waveguides (WGs), primary and trailing echoes (TE) interfere, limiting the number, density, and placement of EFs we can use. We report the design guidelines for creating US-segmented WGs for measuring distributed properties, in which the impact of TEs is minimized or eliminated. Two waveguide designs using these principles have been tested in spatially distributed temperature measurements in high-temperature or restrictive environments.

Walton, Kenneth↗

DOE OSTI2020

Estimation, Minimization, and Validation of Commutation Loop Inductance for a 135-kW SiC EV Traction Inverter

With growing interests in low inductance SiC based power module packaging, it is vital to focus on system level design aspects to facilitate easy integration of the modules and reap system level benefits. To effectively utilize the low inductance modules, busbar and interconnects should also be designed with low stray inductances. A wholistic investigation of the flux path and flux cancellations in the module-busbar assembly which as differentially coupled series inductors is thus mandatory for a system level design. This work presents a busbar design which can be adopted to effectively integrate the CREE’s low inductance 1.2 kV/1.7 kV SiC power modules. The paper also proposes a novel measurement technique to measure the inductance of the modulebusbar assembly as a whole rather than deducing it from individual components. The inductance of the overall commutation loop of the inverter which encompasses the SiC power module, interconnects and PCB busbar have been estimated using finite element analysis (FEA). Furthermore, insights gained from FEA provided the guidelines to decide on the placement of the decoupling capacitors in the busbar to minimize the overall commutation loop inductance from 12.8 nH to 7.4 nH which resulted in significant reduction in the device voltage overshoot. The simulation results have been validated through measurements using an impedance analyzer with less than 5% difference between extracted loop inductance from FEA and measurements. The bus bar design study and the measurement technique discussed in this paper, can be easily extended to other power module packages. Finally, the 135 kW inverter has been compared to a similar highpower inverter utilizing a laminated busbar to highlight the performance of the former.

42 ENGINEERING↗

DOE OSTI2025

Ultraviolet Fluorescence Imaging for Photovoltaic Module Metrology: Best Practices and Survey of Features Observed in Fielded Modules

As the photovoltaics (PV) industry grows in sophistication, so must the extent to which systems are characterized. UV Fluorescence (UVF) imaging is a valuable, easy-to-perform, high-throughput, nonintrusive technique for characterizing modules in the field and in the lab. However, UVF is still a relatively new technique, and many in the PV industry are still unaware of its potential. We provide a guideline for obtaining, processing, and interpreting UVF images. We have provided a list of considerations for imaging hardware and settings, a suggested pipeline for image processing, and details on a survey of features shown in UVF images. As a result, a new database with UVF images of 7190 modules and another database curated by BrightSpot Automation are publicly available.

14 SOLAR ENERGY↗

DOE OSTI2025

Understanding Reliability Trade-Offs in 1T-nC and 2T-nC FeRAM Designs

Ferroelectric random access memory (FeRAM) is a promising candidate for energy-efficient nonvolatile memory, particularly for logic-in-memory and compute-in-memory (CIM) applications. Among the available cell architectures, One-Transistor–n-Capacitor (1T-nC) and two-transistor–n-capacitor (2T-nC) FeRAMs each offer distinct trade-offs in density, scalability, and reliability. In this work, we present a comparative study of these two architectures under both dimensional scaling ( XY/Z shrinkage) and vertical integration (increasing stacked capacitors per cell). Using technology computer-aided design (TCAD) and circuit-level simulations, we analyze how scaling impacts ferroelectric capacitance, parasitic coupling, and floating-node (FN) dynamics, which together dictate sense margin (SM) and read stability. A key mitigation strategy—floating unselected capacitors—is applied to both architectures, effectively decoupling the SM from the number of stacked capacitors and enabling tractable analysis across scaling regimes. Results show that 1T-nC suffers more from charge sharing with the bitline (BL), while 2T-nC benefits from transistor isolation and stronger low-voltage sensing at the cost of increased area. By systematically evaluating these behaviors across scaling directions, this work establishes the reliability trade-offs of 1T-nC and 2T-nC cells and provides design guidelines for high-density, vertically integrated FeRAM systems.

1T-nC↗

DOE OSTI2023

Visualization and Decision Making Design Under Uncertainty

Uncertainty is an important aspect to data understanding. Without awareness of the variability, error, or reliability of a dataset, the ability to make decisions on that data is limited. However, practices around uncertainty visualization remain domain-specific, rooted in convention, and in many instances, absent entirely. Part of the reason for this may be a lack of established guidelines for navigating difficult choices of when uncertainty should be added, how to visualize uncertainty, and how to evaluate its effectiveness. Unsurprisingly, the inclusion of uncertainty into visualizations is a major challenge to visualization. As work concerned with uncertainty visualization grows, it has become clear that simple visual additions of uncertainty information to traditional visualization methods do not appropriately convey the meaning of the uncertainty, pose many perceptual challenges, and, in the worst case, can lead a viewer to a completely wrong understanding of the data. These challenges are the driving motivator for this special issue.

data models↗